engleski

Honey adulteration detection by differential scanning calorimetry (DSC)

Differential Scanning Calorimetry (DSC) has a very broad field of application. DSC is a thermal analysis which can determine a small heat flows, resulting from various structural modifications (transitions) of food compounds, during temperature-programmed scans. Sometimes, it is very useful technique to complement chemical analytical methods which show the limitations of the phisicochemical determinations (i.e. pH, acidity, water activity, conductivity). This technique was used in this study to determine thermal behaviour, energy variation during phase transition (crystalization or/and fusion), glass transition temperature, and water content relationship in honey. This can be of big importance for definition of honey quality and for detecting its alteration or/and adulteration. Honey adulteration (mostly with corn syrups, glucose, sucrose, and others) has appeared on the world market in 1970s, with an industrial development of "high fructose corn syrups". The addition of syrups produces commercial honey with lower quality. DSC was used to follow the thermal behaviour of four authentic (pure) Croatian types of honey from acacia, chestnut, meadow and sage, pure syrup and adulterated honey samples with different amounts of fructose syrup (5, 10, and 20 %). We used DSC to follow the effect of added syrups on the thermal behaviour of pure honey. Thermal or thermophysical parameters such as the glass transition temperature (Tg), entalpies of fusion (DHfus), and heat capacity (DCp) were measured. Experiments were conducted in the temperature range from -100 to 220 °C to obtain the complete thermal behaviour of pure honeys, syrup and artificially adulterated honeys by syrup addition. Addition of syrups resulted in a shift of the glass transition temperatures (onset and midpoint) and increase in the enthalpies of fusion, but variation of the specific heat capacity (DCp) did not appear to be a good parameter for distinguishing between pure and adulterated honeys. DSC parameters showed a detection of fructose syrup presence in authentic honeys at a level of 5 %.

honey; adulteration; thermal behaviour; differential scanning calorimetry

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